From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: X-Spam-Checker-Version: SpamAssassin 3.4.0 (2014-02-07) on aws-us-west-2-korg-lkml-1.web.codeaurora.org X-Spam-Level: X-Spam-Status: No, score=-2.2 required=3.0 tests=HEADER_FROM_DIFFERENT_DOMAINS, MAILING_LIST_MULTI,SPF_HELO_NONE,SPF_PASS,USER_AGENT_SANE_1 autolearn=no autolearn_force=no version=3.4.0 Received: from mail.kernel.org (mail.kernel.org [198.145.29.99]) by smtp.lore.kernel.org (Postfix) with ESMTP id E6661C74A35 for ; Wed, 10 Jul 2019 17:46:05 +0000 (UTC) Received: from vger.kernel.org (vger.kernel.org [209.132.180.67]) by mail.kernel.org (Postfix) with ESMTP id C4250208E4 for ; Wed, 10 Jul 2019 17:46:05 +0000 (UTC) Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1727777AbfGJRqE convert rfc822-to-8bit (ORCPT ); Wed, 10 Jul 2019 13:46:04 -0400 Received: from mail-pg1-f193.google.com ([209.85.215.193]:43121 "EHLO mail-pg1-f193.google.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1727330AbfGJRqE (ORCPT ); Wed, 10 Jul 2019 13:46:04 -0400 Received: by mail-pg1-f193.google.com with SMTP id f25so1575041pgv.10 for ; Wed, 10 Jul 2019 10:46:03 -0700 (PDT) X-Google-DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=1e100.net; s=20161025; h=x-gm-message-state:subject:to:references:from:message-id:date :user-agent:mime-version:in-reply-to:content-language :content-transfer-encoding; bh=BhKBNyGYuDW2lcc8q3UKIy1/Ot87NeMwn9SCW5GMqCM=; b=Esf46IovtUTax+ZrbNQ6jnph6jHDcTUG9KdOZ4QUxZHgU6DsCKtgTciC5I4plH4KtD k+u9j+4urOJOwCUaSYKuXdXdXPakn4FmToL4pyGyTjoA6+81oC/VTCcY11JidCPnNkH5 5Fd5dgtk4f69gihqF4i5hIPdtmAAWd93vOonsRZIZBH6ue2KiuuvTzfKvzgNvE+G0j6x YAdwHAD5kIWwbZESuBHdoAtSW8pZUSJ7WUAlmjWfgbsHCCyk6beP4FM0k56hkaBhid0O TDC0FqlTKUG9LMUJK5IauDoKBC4AwAVV1iLmud+dTOeC0D3fNBoVPn7KLVnlhCdud9IY Hh6w== X-Gm-Message-State: APjAAAUonggeaocuN0zWV2zmab8qGVsv5gUGEFTlffjdl7rBrnmqEtJN BStFamdcldjCYF4HDvgne40= X-Google-Smtp-Source: APXvYqxPI+HXvLvWR0UABwLpNihucLsVrRaMtIocJj++h+5ihAMD9gwgou7eyAZUM53sEiirvMZMkg== X-Received: by 2002:a17:90a:ad41:: with SMTP id w1mr8298926pjv.52.1562780763119; Wed, 10 Jul 2019 10:46:03 -0700 (PDT) Received: from ?IPv6:2620:15c:2c1:200:fb9c:664d:d2ad:c9b5? ([2620:15c:2c1:200:fb9c:664d:d2ad:c9b5]) by smtp.gmail.com with ESMTPSA id r188sm8044323pfr.16.2019.07.10.10.46.01 (version=TLS1_2 cipher=ECDHE-RSA-AES128-GCM-SHA256 bits=128/128); Wed, 10 Jul 2019 10:46:01 -0700 (PDT) Subject: Re: BUG: MAX_STACK_TRACE_ENTRIES too low! (2) To: Peter Zijlstra , Ingo Molnar , Will Deacon , linux-kernel@vger.kernel.org, syzbot , syzkaller-bugs@googlegroups.com References: <00000000000089a718058556e1d8@google.com> <20190710053030.GB2152@sol.localdomain> <20190710170057.GB801@sol.localdomain> <20190710172123.GC801@sol.localdomain> From: Bart Van Assche Message-ID: Date: Wed, 10 Jul 2019 10:46:00 -0700 User-Agent: Mozilla/5.0 (X11; Linux x86_64; rv:60.0) Gecko/20100101 Thunderbird/60.7.2 MIME-Version: 1.0 In-Reply-To: <20190710172123.GC801@sol.localdomain> Content-Type: text/plain; charset=utf-8 Content-Language: en-US Content-Transfer-Encoding: 8BIT Sender: linux-kernel-owner@vger.kernel.org Precedence: bulk List-ID: X-Mailing-List: linux-kernel@vger.kernel.org On 7/10/19 10:21 AM, Eric Biggers wrote: > With my simplified reproducer, on commit 669de8bda87b ("kernel/workqueue: Use > dynamic lockdep keys for workqueues") I see: > > WARNING: CPU: 3 PID: 189 at kernel/locking/lockdep.c:747 register_lock_class+0x4f6/0x580 > > and then somewhat later: > > BUG: MAX_LOCKDEP_KEYS too low! > > If on top of that I cherry pick commit 28d49e282665 ("locking/lockdep: Shrink > struct lock_class_key"), I see instead: > > BUG: MAX_STACK_TRACE_ENTRIES too low! > > I also see that on mainline. > > Alternatively, if I check out 669de8bda87b and revert it, I don't see anything. Hi Eric, Is the rdma_ucm code the only code that triggers the "BUG: MAX_STACK_TRACE_ENTRIES too low!" complaint or is this complaint also triggered by other kernel code? I'm asking this because I think that fixing this would require to implement garbage collection for the stack_trace[] array in the lockdep code. That would make the lockdep code slower. I don't think that making the lockdep code slower would be welcome. Bart.